Manufacturing techniques are known that make it possible to obtain micron-sized metal grids. These have the advantage of attaining surface resistances of less than 1 ohm/square while retaining a light transmission (TL) of around 75 to 85%. However, their production process is based on a technique of etching a metal layer via a photolithographic process resulting in a high manufacturing cost that is incompatible with the envisioned applications.
Document U.S. Pat. No. 7,172,822 itself describes the production of an irregular network conductor that is based on the use of a cracked silica sol-gel mask. In the examples carried out, a sol based on water, alcohol and a silica precursor (TEOS) was deposited, the solvent was evaporated and it was annealed at 120° C. for 30 minutes in order to form the 0.4 μm thick cracked sol-gel mask.
Once the OLED device is produced, aluminum wires are connected to the electrodes for the electrical power supply.
FIG. 3 from this document U.S. Pat. No. 7,172,822 reveals the morphology of the silica sol-gel mask. It appears in the form of fine crack lines oriented along a preferred direction, with bifurcations characteristic of the fracture phenomenon of an elastic material. These main crack lines are occasionally joined together by the bifurcations.
The domains between the crack lines are asymmetric with two characteristic dimensions: one parallel to the crack propagation direction between 0.8 and 1 mm, the other perpendicular between 100 and 200 μm.
This process for manufacturing an electrode by cracking of the sol-gel mask admittedly constitutes progress for the manufacture of a network conductor by eliminating, for example, recourse to photolithography (exposure of a resist to radiation/a beam and development), but may still be improved, especially in order to be compatible with industrial requirements (reliability, simplification and/or reduction of the manufacturing steps, reduced cost, etc.).
It can also be observed that this manufacturing process inevitably requires the deposition of a (chemically or physically) modifiable sublayer at the openings in order either to allow a favored adhesion (of metal colloids for example) or else to allow catalyst grafting for metal postgrowth, this sublayer therefore having a functional role in the growth process of the network.
Furthermore, the profile of the cracks is V-shaped due to the fracture mechanics of the elastic material, thus entailing the use of a post-mask process in order to make the metallic network grow starting from colloidal particles located at the base of the V.
Furthermore, both the electrical and/or optical properties of this irregular network electrode and the connection system and/or other connected functions can be improved.